For RGB bulbs, the device page offers a spiffy selector that uses the browser's native color picker to produce a COLOR_MAP. (The native selector is much spiffier on desktop Chrome than on Android, though.) It looks like the two fields -- the <input type="color".../> and the text input with the resulting HSL map, are bound together by some JS on the page.
Is there an input type we can use to create a similar input mechanism in an app, or would we need to put the color input in a paragraph and then do similar JS acrobatics? (I'd honestly prefer to have only the color picker, since at least the desktop version allows you to enter HSL values directly in that already.)
